Methods and apparatus for fabricating gas turbine engines

ABSTRACT

Methods and apparatus of fabricating gas turbine engine components are provided. The method includes positioning a non-consumable shield adjacent to an edge of the component such that a gap is defined between the shield and the component, wherein the shield and gap form a fluid flow restriction adjacent to the edge, and inducing an electrical current from an anode to the component through an electrolyte bath such that a coating is applied to the component.

BACKGROUND OF THE INVENTION

This invention relates generally to turbine engines, and morespecifically to environmental coatings used with turbine enginecomponents.

At least some known gas turbine engines include a forward fan, a coreengine, and a power turbine. The core engine includes at least onecompressor that provides pressurized air to a combustor wherein the airis mixed with fuel and ignited for generating hot combustion gases. Thecombustion gases flow downstream to one or more turbines that extractenergy therefrom to power the compressor and provide useful work, suchas powering an aircraft. A turbine section may include a stationaryturbine nozzle positioned at the outlet of the combustor for channelingcombustion gases into a turbine rotor disposed downstream thereof.

The turbine nozzle may include a plurality of circumferentially spacedapart vanes. The vanes are impinged by the hot combustion gases exitingthe combustor and are at least partially coated to facilitate protectingthe vanes from the environment and to facilitate reducing wear.Specifically, in at least same engines, a platinum aluminide coating isbe applied to turbine components, including the vanes to facilitateenvironmentally protecting the components. The application of platinumaluminide coatings is generally a three-step process that may include anelectroplating process, a diffusion heat treatment, and an aluminidingprocess. During electroplating, platinum is plated over the surface ofthe component to be coated. Such that an electroplate coat ofsubstantially uniform thickness is applied across the entire surface ofthe component. However, a magnetic field generated by current flowbetween the component to be coated and an anode used in coating may benon-uniformly distributed across the component, and more specificallysuch flux lines may be more dense adjacent sharp edges on the part, suchas adjacent the trailing edge of the nozzle vane. As a result, a thickercoating of plating may be applied to such edges relative to the convexand concave surfaces of the airfoil portion of the vane. Over time, theuneven distribution of coatings may cause cracking: At least one knownmethod of controlling the electroplate thickness adjacent the trailingedge requires that a disposable, metallic “robber” be positionedadjacent to the trailing edge to thieve current from the edge during thecoating application. However, within such methods the effectiveness ofthe robber degrades over time and it may require frequent replacement.

BRIEF DESCRIPTION OF THE INVENTION

In one embodiment, a method of fabricating a gas turbine enginecomponent are provided. The method includes positioning a non-consumableshield adjacent to an edge of the component such that a gap is definedbetween the shield and the component, wherein the shield and gap form afluid flow restriction adjacent to the edge, and inducing an electricalcurrent from an anode to the component through an electrolyte bath suchthat a coating is applied to the component.

In another embodiment, an electroplating apparatus is provided. Theelectroplating apparatus includes an electroplating bath that includesan electrolytic solution, a power source, an anode coupled to the powersource, a component coupled to the power source and immersed within theelectrolytic solution wherein the component includes a plating surfacebordered by an edge, and a non-consumable shield positioned adjacent tothe component edge such that a gap is defined between the edge and theshield and wherein the shield and the gap form a fluid flow restrictionadjacent to the edge.

In yet another embodiment, an electroplating apparatus is provided. Theelectroplating apparatus includes an electroplating bath including anelectrolytic solution comprising platinum, a power source, an anodecoupled to the power source, a component to be electroplated coupled tothe power source and immersed within the electrolytic solution whereinthe component includes a plating surface and an edge, and anon-consumable shield positioned adjacent to the edge such that a gap isdefined between the edge and the shield and wherein the shield and thegap form a fluid flow restriction adjacent to the edge. The shield isconfigured to displace an electric field away from the edge tofacilitate reducing an amount of electroplating deposited on the edge.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of an exemplary highbypass ratio turbofan engine;

FIG. 2 is a perspective view of an exemplary first stage, high pressureturbine nozzle segment that may be used with the gas turbine engine(shown in FIG. 1);

FIG. 3 is a perspective view of an exemplary electroplating process forapplying an electroplate coating to the vanes shown in FIG. 2.

FIG. 4 is a cross-sectional view of high pressure turbine nozzle vane118 that may be used in the electroplating process shown in FIG. 3; and

FIG. 5 is a graph of electroplate coating thickness readings taken ateach of the plurality of test locations shown in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term “component” may include any componentconfigured to be coupled with a gas turbine engine that may be coatedwith a metallic film coating, for example a high pressure turbine nozzlevane. A high pressure turbine nozzle vane is intended as exemplary only,and thus is not intended to limit in any way the definition and/ormeaning of the term “component”. Furthermore, although the invention isdescribed herein in association with a gas turbine engine, and morespecifically for use with a high pressure turbine nozzle vane for a gasturbine engine, it should be understood that the present invention isapplicable to other gas turbine engine stationary components androtatable components. Accordingly, practice of the present invention isnot limited to high pressure turbine nozzle vanes for a gas turbineengine. In addition, although the invention is described herein inassociation with a electrolytic bath process, it should be understoodthat the present invention may be applicable to any electroplatingprocess, for example, brush electroplating. Accordingly, practice of thepresent invention is not limited to an electroplating process using anelectrolytic bath.

FIG. 1 is a longitudinal cross-sectional view of an exemplary highbypass ratio turbofan engine 10. Engine 10 includes, in serial axialflow communication about a longitudinal centerline axis 12, a fan 14, abooster 16, a high pressure compressor 18, a combustor 20, a highpressure turbine 22, and a low pressure turbine 24. High pressureturbine 22 is drivingly connected to high pressure compressor 18 with afirst rotor shaft 26, and low pressure turbine 24 is drivingly connectedto booster 16 and fan 14 with a second rotor shaft 28.

During operation of engine 10, ambient air passes through fan 14,booster 16, and compressor 18, the pressurized air stream enterscombustor 20 where it is mixed with fuel and burned to provide a highenergy stream of hot combustion gases. The high-energy gas stream passesthrough high-pressure turbine 22 to drive first rotor shaft 26. The gasstream passes through low-pressure turbine 24 to drive second rotorshaft 28, fan 14, and booster 16. Spent combustion gases exit out ofengine 10 through an exhaust duct (not shown).

It should be noted that although the present description is given interms of a turbofan aircraft engine, embodiments of the presentinvention may be applicable to any gas turbine engine power plant suchas that used for marine and industrial applications. The description ofthe engine shown in FIG. 1 is only illustrative of the type of engine towhich some embodiments of the present invention is applicable.

FIG. 2 is a perspective view of an exemplary first stage, high pressureturbine nozzle segment 114 that may be used with the gas turbine engine10 (shown in FIG. 1). High pressure turbine nozzle segment 114 may bepositioned axially between combustor 20 and high pressure turbine 22such that a row of first stage turbine rotor blades (not shown) ispositioned downstream from high pressure turbine nozzle segment 114. Aplurality of high pressure turbine nozzles 114 may be circumferentiallyspaced about axis 12 to form a high pressure turbine nozzle (not shown).High pressure turbine nozzle segment 114 includes at least one nozzlevane 118 coupled at opposite radial ends to a respective radially innerband 120 and a respective radially outer band 122. High pressure turbinenozzle segment 114 are typically formed in arcuate segments having twoor more vanes 118 per segment 114. Vanes 118 may be cooled duringoperation against a flow of hot combustion gases 116 using a flow ofcooling air 124 that may be channeled from, for example, a discharge ofcompressor 18 to individual vanes 118 through outer band 122.

Each vane 118 includes a generally concave pressure sidewall 126, and acircumferentially opposite generally convex, suction sidewall 128.Sidewalls 126 and 128 may extend longitudinally in span along a radialaxis of the nozzle between bands 120 and 122 wherein a root 130 couplesto inner band 120 and a tip 132 couples to outer band 122. Sidewalks 126and 128 extend chorale or axially between a leading edge 134 and anopposite trailing edge 136.

FIG. 3 is a perspective view of an exemplary electroplating process 200for applying an electroplate coating to vanes 118 (shown in FIG. 2). Inthe exemplary embodiment, vane 118 may energized to a predeterminednegative voltage with respect to a grid 202 such that when anelectrolyte solution containing metal ions, for example, platinum coversa surface of vane 118, for example, sidewall 126, the metal ions in theelectrolyte solution may be preferentially attracted to and bonded tosidewall 126 to form an electroplate coating 204. In the exemplaryembodiment, a non-conducting, non-consumable shield 206 is positionedadjacent trailing edge 136 such that a longitudinal axis 208 of shield206 is substantially parallel to trailing edge 136 and separated by agap 210 having a predetermined distance 212. In the exemplaryembodiment, distance 212 is approximately thirty mils. In an alternativeembodiment, distance 212 is a distance greater than or less then thirtymils. In the exemplary embodiment, shield 206 is fabricated from anon-conducting material, for example, plastic and has an outsidediameter 218, for example, three-quarters inches, that is substantiallygreater than the thickness 220 of vane 118 at trailing edge 136. Therelatively larger diameter of shield 206 with respect to the thicknessof trailing edge 136 substantially blunts the geometry of trailing edge136 and facilitates blocking at least a portion of the electricalcurrent through trailing edge 136. Additionally, the close clearance ofdistance 212 to trailing edge 136 facilitates reducing a flow ofelectrolyte solution proximate trailing edge 136. Shield 206 may beformed to follow the contour of an irregularly shaped or curved edgewhile maintaining gap distance 212. Additionally, shield 206 may includean irregular cross-section, for example, shield 206 may be a hollow orsolid and may include a groove or slot configured to be aligned withedge 136 for optimizing the flow restrictive gap distance 212 and/or theelectrical characteristics of the electric field proximate gap distance212.

FIG. 4 is a cross-sectional view of high pressure turbine nozzle vane118 that may be used in electroplating process 200 (shown in FIG. 3).Vane 118 includes concave pressure sidewall 126 and convex suctionsidewall 128 that each extend axially between leading edge 134 andtrailing edge 136. A plurality of thickness test locations are locatedat predetermined locations about a perimeter of vane 118 and are labeled401-410.

FIG. 5 is a graph 500 of electroplate coating thickness readings takenat each of the plurality of test locations 401-410 (shown in FIG. 4).Graph 500 includes an x-axis 502 whose units correlate with eachrespective test location, 401-410 (shown in FIG. 4). For example,electroplate coating thickness reading 401 is taken proximate leadingedge 134, electroplate coating thickness reading 406 is taken proximatetrailing edge 136, and electroplate coating thickness readings 404 and409 are taken proximate convex side 128 and proximate concave side 126respectively. A y-axis 504 may be graduated in units of mils indicativeof a thickness of a plating coating corresponding to the respectivelocation, 401-410.

In the exemplary embodiment, a trace 506 joins points on graph 500corresponding to an exemplary electroplate process for coating nozzlevane 118 with a metallic film coating. Trace 506 illustrates readingstaken using the electroplate process wherein shield 206 is not utilizedto form a flow restrictive gap distance 212 adjacent edge 136. Trace 506illustrates a metallic film coating thickness at location 406 that isapproximately 100% greater than the metallic film coating thickness atlocations 401-405 and 407-410.

A trace 508 illustrates readings taken at locations 401-410 after usingthe electroplate process wherein shield 206 is utilized to form a flowrestrictive gap distance 212 adjacent edge 136 and to displace anelectric field adjacent edge 136. Shield 206 facilitates plating auniform metallic film coating thickness at locations 401-410. Trace 506illustrates a metallic film coating thickness at location 406 that isapproximately only 25% greater than the metallic film coating thicknessat locations 401-405 and 407-410. Using shield 206 results in a moreuniform metallic film coating thickness around the perimeter of vane118.

A thickness ration may be defined as a ratio of a maximum thickness fromlocations around the perimeter of the airfoil (t_(max)) to a minimumthickness (t_(min)),$\text{Thickness~~Ratio} = {\frac{t_{MAX}}{t_{MIN}}.}$

Trace 508 exhibits a thickness ratio of approximately 1.94, using theabove formula, while trace 506 exhibits a thickness ratio ofapproximately 3.03, which represents a 40% improvement in uniformity ofthe metallic film coating thickness about the perimeter of vane 118.

The above-described methods and apparatus are cost-effective and highlyreliable for providing a substantially uniform metallic film coatingthickness on gas turbine engine components, such as a high pressureturbine first stage nozzle. Specifically, the shield positioned adjacentthe edge of the nozzle vane to be coated, defines an electrolyte flowrestrictive gap and displaces a portion of the electric field adjacentthe edge. Restricting the electrolyte flow adjacent the edge permits theelectrolyte to be depleted in the gap and reduces the metallic ionconcentration available for plating the edge. Displacing a portion ofthe electric field adjacent the edge facilitates reducing theelectroplating motive force and thus, the rate of plating on the edge.The methods and apparatus facilitate fabrication of machines, and inparticular gas turbine engines, in a cost-effective and reliable manner.

Exemplary embodiments of electroplating methods and apparatus componentsare described above in detail. The components are not limited to thespecific embodiments described herein, but rather, components of eachapparatus may be utilized independently and separately from othercomponents described herein. Each electroplating method and apparatuscomponent can also be used in combination with other electroplatingmethods and apparatus components.

While the invention has been described in terms of various specificembodiments, those skilled in the art will recognize that the inventioncan be practiced with modification within the spirit and scope of theclaims.

1. A method of fabricating a gas turbine engine component, said methodcomprising: positioning a non-consumable shield adjacent to an edge ofthe component such that a gap is defined between the shield and thecomponent, wherein the shield and gap form a fluid flow restrictionadjacent to the edge; and inducing an electrical current from an anodeto the component through an electrolyte bath such that a coating isapplied to the component.
 2. A method in accordance with claim 1 furthercomprising electroplating the component such that a thickness of theplating coating on the edge of the component is substantially equal to athickness of the plating coating across the surface of the component. 3.A method in accordance with claim 1 wherein inducing an electricalcurrent from an anode to the component comprises coupling the componentas a cathode in the electrical circuit.
 4. A method in accordance withclaim 1 wherein positioning a non-consumable shield adjacent to an edgeof the component comprises positioning a non-conductive shield adjacentto the edge such that at least a portion of an electric field generatedis displaced away from the edge.
 5. A method in accordance with claim 1wherein positioning a non-consumable shield adjacent to an edge of thecomponent comprises selecting a size of the shield to facilitatedisplacing an electric field away from the edge, such that the coatingdeposited on the edge is substantially uniform with respect to thecoating deposited on the component.
 6. A method in accordance with claim1 wherein positioning a non-consumable shield adjacent to an edge of thecomponent comprises positioning a non-conductive shield adjacent to theedge of the component.
 7. A method in accordance with claim 1 whereinpositioning a non-consumable shield adjacent to an edge of the componentcomprises positioning a shield adjacent to the edge of the componentsuch that a width of the gap is equal to between approximately 0.010inches and approximately 0.050 inches.
 8. A method in accordance withclaim 1 wherein positioning a non-consumable shield adjacent to the edgeof the component comprises positioning the shield adjacent to the edgeof the component such that a width of the gap is equal to approximately0.030 inches.
 9. A method in accordance with claim 1 wherein positioninga non-consumable shield adjacent to the edge of the component comprisespositioning the shield adjacent to the edge, such that the shield has acontour that substantially matches a contour of the edge.
 10. Anelectroplating apparatus comprising: an electroplating bath comprisingan electrolytic solution; a power source; an anode coupled to said powersource; a component coupled to said power source and immersed withinsaid electrolytic solution, said component comprising a plating surfacebordered by an edge; and a non-consumable shield positioned adjacentsaid component edge such that a gap is defined between said edge andsaid shield, said shield and said gap forming a fluid flow restrictionadjacent to said edge.
 11. An electroplating apparatus in accordancewith claim 10 wherein said component is coupled to said power source asa cathode.
 12. An electroplating apparatus in accordance with claim 10wherein said shield is fabricated from a non-conductive material.
 13. Anelectroplating apparatus in accordance with claim 10 wherein said shieldis fabricated from a plastic material.
 14. An electroplating apparatusin accordance with claim 10 wherein said shield is configured todisplace at least a portion of an electric field generated away fromsaid edge.
 15. An electroplating apparatus in accordance with claim 10wherein said shield is configured to facilitate substantially uniformlyplating a metallic film over said plating surface and said edge.
 16. Anelectroplating apparatus in accordance with claim 10 wherein a width ofsaid gap is equal to between approximately 0.010 inches andapproximately 0.050 inches.
 17. An electroplating apparatus inaccordance with claim 10 wherein a width of said gap is approximately0.030 inches.
 18. An electroplating apparatus comprising: anelectroplating bath comprising an electrolytic solution comprisingplatinum; a power source; an anode coupled to said power source; acomponent to be electroplated coupled to said power source and immersedwithin said electrolytic solution, said component comprising a platingsurface and an edge; and a non-consumable shield positioned adjacentsaid edge such that a gap is defined between said edge and said shield,said shield and said gap forming a fluid flow restriction adjacent tosaid edge, said shield configured to displace an electric field awayfrom said edge to facilitate reducing an amount of electroplatingdeposited on said edge.
 19. An electroplating apparatus in accordancewith claim 18 wherein said shield is sized to have a diameter that islarger than said diameter of said edge.
 20. An electroplating apparatusin accordance with claim 18 wherein said shield comprises a body havinga contour that is substantially similar to a contour of said edge suchthat a width of said gap is substantially constant along said edge.